Method of joining diamond to metal



United States Patent Claims priority, application Netherlands, Aug. 29, 1961,

268,734 6 Claims. (Cl. 29473.1)

This invention relates to a method of satisfactorily joining diamond to metal, for example, for manufacturing tools such as drills and chisels, and gramophone reproducing needles.

It is known that metals do not usually provide satisfactory junctions to diamond. This is mostly due to the fact that in the fluid state they do not wet the diamond or wet it inadequately.

Favourable exceptions in this respect are the metals titanium and zirconium which, as is well-known, are used to this end as an intermediate layer. These metals were applied to diamond surfaces for example, by decomposition in vacuo from the hydrides, a further junction being established thereon with the aid of a coppersilver solder.

It is also known that a satisfactory junction to diamond can be obtained directly if use is made of a copper-silver alloy having a titanium content.

The use of titanium and zirconium has the disadvantage that in the presence of air these metals readily enter into reaction while forming oxides and nitrides whereupon they are no longer capable of assisting in wetting the diamond. Consequently, in these cases, satisfactory junctions can only be obtained by using a high vacuum of at least 10- mm. of Hg, or an atmosphere of rare gas containing only a few p.p.m. of impurity.

Such ditficulties also occur when using the said titaniumcontaining solder alloys. Moreover the majority of materials are chemically attacked by these alloys in the matter state, which causes complications in manufacturing and working up these alloys.

Finally, the use of titanium or zironium as an intermediate layer has a further limitation in that the solder to be used thereon must be of a composition such that a sufiiciently matched coefficient of expansion can be obtained. This is also the case with the titanium-containing soldering alloys applied directly to the diamond.

The invention has for its object to mitigate the abovementioned drawbacks.

According to the invention a very satisfactorily adhering junction of a diamond to metal is obtained with the aid of an alloy of gold and at least 1% by weight of tantalum and/ or columbium.

Since these alloys are not particularly reactive, the melting operation may be effected in a less high vacuum, for example 10* nun. of Hg, or in a rare-gas atmosphere of lower purity, than is the case with titanium or zircon-ium.

Alloys having a content of tantalum or niobium lower than approximately 1% by weight do not wet the diamond surface sufliciently. A tantalum content exceeding 25% by weight is usually undesirable since such an alloy has too high a melting point, namely above 1500 C.,

3,192,62h Patented July 6, 1965 or is too brittle. Particularly satisfactory results are obtained with alloys having a tantalum content from 5% to 10% by weight, which flow out very smoothly on the diamond surface and have melt-ing points of approximately ll00 C. to 1300 C.

With a view to the increasing brittleness, the columbium content of the alloys had better not be raised higher than to approximately 10% by Weight. Preferably, the content is chosen lower than about 5% by weight.

With the aid of the alloys of gold and tantalum and/ or columbium, diamond may be soldered to the most widely varying materials, irrespective of their coefiicients of expansion. Suitable for use are, for example, quartz, silicon carbide, ceramic materials and metals such as molybdenum, tungsten and nickel. 1

The fact that in all these cases a junction of great rigidity is obtained which is not or substantially not sensitive to considerable temperature variations as already occur, for example, during cooling when the junction is manufactured, is possible connected with the ductility of the alloys concerned.

This property entails the further advantage that the alloys may readily be shaped into foil or wire, which may be useful in Working up.

Examples (1) When a gramophone reproducing needle is manufactured, one proceeds as follows:

A small diamond is degreased and clamped to one end of a molybdenum rod with the aid of a coiled spring of molybdenum wire. Subsequently, this end is immersed in vacuo or in an argon atmosphere into a molten alloy of 97% by weight of gold and 3% by weight of tantalum for one second at a temperature of approximately 1300 C. The alloy flows smoothly on the diamond and on the molybdenum. Subsequently, the diamond, which is very intimately connected to the molybdenum, is ground.

A similar result is achieved when using an alloy consisting of 97% by weight of gold and 3% by weight of columbiun.

(2) A chisel is manufactured by securing a diamond plate having a surface area of approximately A sq. cm. to a smoothly worked side face of a rod-shaped molybdenum holder with the aid of an alloy comprising by weight of gold and 5% by weight of tantalum. The alloy is applied in the form of a foil approximately microns thick.

A piece of this foil a little larger than the surface of the diamond is laid on the molybdenum, the diamond being placed thereon so as to project partly from the holder.

Subsequently, the assembly is heated in vacuo to approximately 1400 C. with the aid of an inductive highfrequency generator while the diamond in this position is urged on the holder by a pin of ceramic material on a base of alumina.

What is claimed is:

1. A method of joining diamond to a metal comprising applying an alloy selected from the group consisting of gold-tantalum alloys containing from 1% to 25% by weight of tantalum and gold-columbium alloys containing from 1% to 10% by weight of columbium to opposing surfaces of said diamond and metal and melting said alloy in an inert atmosphere.

'i v 0 L 2. The method of claim 1 wherein the alloy consists group consisting of gold-tantalum alloys containing from of gold and from 1% to 25% by weight of tantalum. 1% to 25% by weight of tantalum and gold-columbium 3. The method of claim 1 wherein the alloy consists alloys containing from 1% by 10% by Weight of tantalum.

of gold and from 5% to 10% by weight of tantalum.

4. The method of claim 1 wherein the alloy consists References Cited by the Examiner of gold and from 1% to 10% by Weight of columbium. UNITED STATES PATENTS 5. The method of claim 1 wherein the alloy consists 2,739,375 3/56 Coxe 29 473'1 X of gold and from 1% to 5% by Weight of columbium. 2 979 13 l 4 1 s i 29 472 9 X 6. An article comprising diamond soldered to a metal object, said solder consisting of an alloy selected from the 10 JOHN F. CAMPBELL, Primary Examiner. 

1. A METHOD OF JOINING DIAMOND TO A METAL COMPRISING APPLYING AN ALLOY SELECTED FROM THE GROUP CONSISTING OF GOLD-TANTALUM ALLOYS CONTAINING FROM 1% TO 25% BY WEIGHT OF TANTALUM AND GOLD-COLUMBIUM ALLOYS CONTAINING FROM 1% TO 10% BY WEIGHT OF COLUMBIUM TO OPPOSING SURFACES SAID DIAMOND AND METAL AND MELTING SAID ALLOY IN AN INERT ATMOSPHERE.
 6. AN ARTICLE COMPRISING DIAMOND SOLDERED TO A METAL OBJECT, SAID SOLDER CONSISTING OF AN ALLOY SELECTED FROM THE GROUP CONSISTING OF GOLD-TANTALUM ALLOYS CONTAINING FROM 1% TO 25% BY WEIGHT OF TANTALUM AND GOLD-COLUMBIUM ALLOYS CONTAINING FROM 1% TO 10% BY WEIGHT OF TANTALUM. 